feat(members): implement /members page — Kachel-Ansicht (E2, issue #48)

Backend:
- Rename V006 migration to V026 (avoid conflict with existing V006)
- Migration adds invalidated_at + partial unique index on household_invite

Frontend:
- Toast.svelte — new system component (message + dismiss)
- SegmentedControl.svelte — new system component (options, value, onchange)
- members/+page.server.ts — loads members + active invite
- members/[userId]/+server.ts — DELETE/PATCH proxy
- members/invites/+server.ts — POST (regenerate) proxy
- MemberCard.svelte — tile with avatar, kebab, inline role edit
- RemoveDialog.svelte — confirmation dialog (desktop modal + BottomSheet mobile)
- InviteCard.svelte + InvitePanel.svelte — invite management UI
- MemberGrid.svelte — responsive 4/2-col grid with sorted members
- members/+page.svelte — page composing all components with optimistic updates

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/routes/(app)/members/page.server.test.ts

@@ -0,0 +1,74 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+
+vi.mock('$lib/server/api', () => ({
+	apiClient: vi.fn(() => ({
+		GET: vi.fn()
+	}))
+}));
+
+vi.mock('$env/dynamic/private', () => ({ env: { BACKEND_URL: 'http://localhost:8080' } }));
+
+describe('members page.server load', () => {
+	let load: any;
+
+	beforeEach(async () => {
+		vi.resetModules();
+		const mod = await import('./+page.server');
+		load = mod.load;
+	});
+
+	it('returns members and currentUserId', async () => {
+		const mockGet = vi.fn().mockImplementation((path: string) => {
+			if (path === '/v1/households/mine/members') {
+				return {
+					data: [
+						{ userId: 'u1', displayName: 'Sarah', role: 'planner', joinedAt: '2024-01-01T00:00:00Z' },
+						{ userId: 'u2', displayName: 'Tom', role: 'member', joinedAt: '2024-02-01T00:00:00Z' }
+					]
+				};
+			}
+			if (path === '/v1/households/mine/invites') {
+				return {
+					data: {
+						data: {
+							inviteCode: 'ABC123',
+							shareUrl: 'https://x.com/join/ABC123',
+							expiresAt: '2024-12-01T00:00:00Z'
+						}
+					}
+				};
+			}
+			return { data: null };
+		});
+
+		const { apiClient } = await import('$lib/server/api');
+		(apiClient as ReturnType<typeof vi.fn>).mockReturnValue({ GET: mockGet });
+
+		const result = await load({
+			fetch: vi.fn(),
+			locals: { benutzer: { id: 'u1', name: 'Sarah', email: 'sarah@example.com' }, haushalt: {} }
+		} as any);
+
+		expect(result.members).toHaveLength(2);
+		expect(result.currentUserId).toBe('u1');
+		expect(result.activeInvite).toBeDefined();
+	});
+
+	it('returns null activeInvite when no active invite exists', async () => {
+		const mockGet = vi.fn().mockImplementation((path: string) => {
+			if (path === '/v1/households/mine/members') return { data: [] };
+			if (path === '/v1/households/mine/invites') return { data: null };
+			return { data: null };
+		});
+
+		const { apiClient } = await import('$lib/server/api');
+		(apiClient as ReturnType<typeof vi.fn>).mockReturnValue({ GET: mockGet });
+
+		const result = await load({
+			fetch: vi.fn(),
+			locals: { benutzer: { id: 'u1', name: 'Sarah', email: 'sarah@example.com' }, haushalt: {} }
+		} as any);
+
+		expect(result.activeInvite).toBeNull();
+	});
+});